An age-sex pyramid is a bar chart graphically representing the age structure of the population, usually in five-year age groups, for males and females separately. The age structure of the population usually approximates the shape of a pyramid because mortality progressively reduces the number in each birth cohort as it ages. The age pyramid is useful to show the existence of unusually large or small cohorts, and in this way, not only conveys information about a country's past demographic history, but also a great deal about its demographic future.

Ageing of the population

Ageing of the population is the consideration of the proportion of the population aged 65 years and over, and the way this proportion is continuing to increase, mostly due to persistent low fertility rates and declining mortality rates.

Age-specific fertility rates

Age-specific fertility rates (ASFR) are the number of live births (occurred or registered) during the calendar year, according to the age of the mother, per 1,000 of the female estimated resident population of the same age at 30 June. For calculating these rates, births to mothers under 15 years are included in the 15-19 years age group, and births to mothers aged 50 years and over are included in the 45-49 years age group. Pro rata adjustment is made for births for which the age of the mother is not given.

Average annual growth rate

The average annual growth rate, r, is calculated as a percentage using the formula:

where P0 is the population at the start of the period, Pn is the population at the end of the period and n is the length of the period between P0 and Pn in years.

Baby boom

Baby boom refers to the generation born between the end of World War II and the mid-1960s. Baby boomers are usually taken to be those born in the years 1946 to 1965 inclusive.

Balance of state or territory

The aggregation of all Statistical Divisions (SD) within a state or territory other than its Capital City SD. See Major Statistical Region in Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).

Birth

The delivery of a child, irrespective of the duration of pregnancy, who, after being born, breathes or shows any evidence of life such as heartbeat.

Capital city

Refers to the Capital City Statistical Divisions of states and territories as defined in the Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).

Completed fertility

Completed fertility represents the average number of births a cohort of females have borne over their reproductive lifetimes.

Confinement

A pregnancy which results in at least one live birth.

Crude birth rate

The crude birth rate is the number of live births registered during the calendar year per 1,000 estimated resident population at 30 June of that year. For years prior to 1992, the crude birth rate was based on the mean estimated resident population for the calendar year.

Estimated resident population (ERP)

The official measure of the population of Australia is based on the concept of residence. It refers to all people, regardless of nationality or citizenship, who usually live in Australia, with the exception of foreign diplomatic personnel and their families. It includes usual residents who are overseas for less than 12 months. It excludes overseas visitors who are in Australia for less than 12 months.

Exnuptial birth

An exnuptial birth is the birth of a child whose parents are not legally married to each other at the time of the child's birth.

Indigenous

Persons who identify themselves as being of Aboriginal or Torres Strait Islander origin.

Indigenous birth

The birth of a live-born child where either the mother or the father was identified as being of Aboriginal or Torres Strait Islander origin on the birth registration form.

Indigenous origin

Persons who identify as being of Aboriginal or Torres Strait Islander origin.

Intercensal discrepancy

Intercensal discrepancy is the difference between two estimates at 30 June of a census year population, the first based on the latest census and the second arrived at by updating the 30 June estimate of the previous census year with intercensal components of population change which take account of information available from the latest census. It is caused by errors in the start and/or finish population estimates and/or in estimates of births, deaths or migration in the intervening period which cannot be attributed to a particular source.

Marital status

Two separate concepts of marital status are measured by the Australian Bureau of Statistics. These are registered marital status and social marital status.

Registered marital status refers to formally registered marriages and divorces. Registered marital status is a person's relationship status in terms of whether he or she has, or has had, a registered marriage with another person. Accordingly, people are classified as either 'never married', 'married', widowed' or 'divorced'.

Social marital status is the relationship status of an individual with reference to another person who is usually resident in the household. A marriage exists when two people live together as husband and wife, or partners, regardless of whether the marriage is formalised through registration. Individuals are, therefore, regarded as married if they are in a de facto marriage, or if they are living with the person to whom they are registered as married. Under social marital status, a person is classified as either 'married' or 'not married' with further disaggregation of 'married' to distinguish 'registered married' from 'de facto married' person.

Median age at childbearing

The term refers to the age at which approximately one-half of the females in a population have their children, either for a birth of particular birth order or for all births. It measures the age at childbearing within the female population, as distinct from the median age of mother at confinement which measures the median age of the females who gave birth in a particular year.

Median age of mother at confinement

The median age of mother at confinement measures the median age of females who gave birth in a particular year.

Median value

For any distribution the median value (age, duration, interval) is that value which divides the relevant population into two equal parts, half falling below the value, and half exceeding it. Where the value for a particular record has not been stated, that record is excluded from the calculation.

Mortality

Death.

Multiple birth

A multiple birth is a confinement which results in two or more children, at least one of which is live-born.

Natural increase

Excess of births over deaths.

Net overseas migration (NOM)

Net overseas migration is the net gain or loss of population through immigration to Australia or emigration from Australia. It is:

based on an international travellers' duration of stay being in or out of Australia for 12 months or more;

the difference between the number of incoming travellers who stay in Australia for 12 months or more and are added to the population and the number of outgoing travellers who leave Australia for 12 months or more and are subtracted from the population.

Net population growth

For Australia, net population growth is the sum of natural increase and net overseas migration. For the states and territories, net population growth also includes net interstate migration.

Net reproduction rate

The net reproduction rate represents the average number of daughters that would be born to a group of females if they are subject to the fertility and mortality rates of a given year during their future life. It indicates the extent to which the population would reproduce itself. The net reproduction rate is obtained by multiplying the age-specific birth rates (for female births only) by the proportion of survivors at corresponding ages in a life table and adding the products.

Nuptial birth

A nuptial birth is the birth of a child born of parents who are legally married at the time of the child's birth.

Nuptial first confinement

A nuptial first confinement is the first confinement in the current marriage and therefore does not necessarily represent the woman's first ever confinement resulting in a live birth.

Nuptiality

Nuptiality relates to the registered marital status of persons and the events such as marriages, divorces and widowhood. Confinements and births are identified as being nuptial where the father registered was married to the mother at the time of birth, or where the husband died during pregnancy. Confinements and children of Indigenous mothers considered to be tribally married are classified as nuptial. Other confinements, and the children resulting from them, are classified as exnuptial whether or not both parents were living together at the time of birth.

Parity

Parity refers to the number of live births a woman has had previous to the most recent birth. Parity is also an attribute of any live birth, being the order of that birth (e.g. first birth, second birth, and so on) of a woman.

Part of state

Part of state is used to refer to the remainder of a state outside the Capital City Statistical Division (SD). See also Balance of state or territory.

Paternity acknowledged birth

A paternity acknowledged birth refers to an exnuptial birth where paternity was acknowledged.

Paternity not acknowledged birth

A paternity not acknowledged birth refers to an exnuptial birth where paternity was not acknowledged.

Population growth

For Australia, population growth is the sum of natural increase and net overseas migration. For states and territories, population growth also includes net interstate migration. After the census, intercensal population growth also includes an allowance for intercensal discrepancy.

Previous births

Previous births refer to children born alive (who may or may not be living) to a mother prior to the registration of the current birth in the processing period. In some states, legitimised and legally adopted children may also be included.

Due to variation in data collection and processing methods across states and territories, different definitions of the concept of previous births have been applied.

Changes in ABS processing of data collected by state/territory Registrars of Births, Deaths and Marriages for 2007 have resulted in the availability of improved information on previous births to mothers. Prior to 2007, ABS published information on previous births of the mother from the current relationship only, for all states and territories. From 2007, data on previous births for all relationships (both current and previous, if any) of the mother are collected for all states and territories, excluding Victoria and Queensland.

Previous children

See Previous births.

Rate of population growth

Population change over a period as a proportion (percentage) of the population at the beginning of the period.

Registered marital status

Registered marital status refers to formally registered marriages for which the partners hold a marriage certificate. In this publication the distinction is between married parents (nuptial births) and unmarried parents (exnuptial births).

Replacement fertility

Replacement level fertility is the number of babies a female would need to have over her reproductive life span to replace herself and her partner. Given the current mortality of females up to age 49 years, replacement fertility is estimated at around 2.1 babies per female.

Sex ratio

The sex ratio relates to the number of males per 100 females. The sex ratio is defined for total population, at birth, at death and among age groups by appropriately selecting the numerator and denominator of the ratio.

Social marital status

Social marital status is the consensual union status of a person with reference to another person in the household. In this publication data are only available from midwives' collection. The categories are married/de facto; single; and separated/divorced/widowed.

State or territory of registration

State or territory of registration refers to the state or territory in which the event was registered.

State or territory and Statistical Local Area (SLA) of usual residence

State or territory and Statistical Local Area (SLA) of usual residence refers to the state or territory and SLA of usual residence of:

the population (estimated resident population)

the mother (birth collection)

the deceased (death collection).

Statistical Division (SD)

Statistical Divisions (SD) consist of one or more Statistical Subdivisions (SSD). The divisions are designed to be relatively homogeneous regions characterised by identifiable social and economic units within the region, under the unifying influence of one or more major towns or cities. Further information concerning SDs is contained in Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).

Statistical Local Area (SLA)

Statistical Local Areas (SLA) are, in most cases, identical with, or have been formed from a division of, whole Local Government Areas (LGA). In other cases, they represent unincorporated areas. In aggregate, SLAs cover the whole of a state or territory without gaps or overlaps. In some cases legal LGAs overlap statistical subdivision boundaries and therefore comprise two or three SLAs (Part A, Part B and, if necessary, Part C). Further information concerning SLAs is contained in Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).

Statistical Subdivision (SSD)

In aggregate, Statistical Subdivisions (SSD) cover the whole of Australia without gaps or overlaps. They are defined as socially and economically homogeneous regions characterised by identifiable links between the inhabitants. In the non-urban areas an SSD is characterised by identifiable links between the economic units within the region, under the unifying influence of one or more major towns or cities. Further information concerning SSDs is contained in Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).

Total fertility rate

The sum of age-specific fertility rates (live births at each age of mother per female population of that age). It represents the number of children a female would bear during her lifetime if she experienced current age-specific fertility rates at each age of her reproductive life.

Usual residence

Usual residence within Australia refers to that address at which the person has lived or intends to live for a total of six months or more in a given reference year.

Year of occurrence

Data presented on year of occurrence basis relate to the date the event occurred.

Year of registration

Data presented on year of registration basis relate to the date the event was registered.

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